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The USB-C power meter is handily colour-matched to your silver MacBook.

Every possible angle, just so you can see how round and silver it is. I love a bit of injection moulded plastic.

There will be many obstacles on the way to the promised single cable type USB-C utopia: new standards that aren't backwards compatible; USB-C sockets that outwardly look the same, but aren't functionally the same; and, of course, dodgy USB-C cables that can fry your exceedingly expensive Chromebook Pixel or MacBook laptop. In the mean time, might I recommend a healthy dose of vigilance, some branded USB-C cables and chargers, and if you're feeling fancy, perhaps a USB-C power meter?

Satechi, which makes a range of reasonably well-reviewed USB cables, hubs, and peripherals, has just released a USB-C power meter ($30, or about £35 delivered to the UK). There are lots of good USB power meters on the market for older USB sockets and standards, but this appears to be the first true USB-C meter (earlier meters aren't rated to the full 5A/20V requirements of USB Power Delivery 2.0).

The Satechi meter will tell you how much electricity is actually flowing into your device in terms of volts, amps, and milliamp-hours (mAh). There's also a little arrow that indicates which side of the dongle is currently being charged; for example, it would point towards a laptop while it's being charged from a wall socket, and then when you swap the cable to your smartphone, to charge it up from the laptop, the arrow would point away.

The voltage and amperage figures might be useful for detecting whether the charging circuit is operating correctly: if the numbers fluctuate, or they seem well below what the device should be capable of drawing, then there could be an issue with the charger, cable, or device (a bad battery, a bad USB controller that isn't negotiating with the charger correctly, etc.) The mAh counter is somewhat handy for testing the true capacity of a portable battery pack, or perhaps to measure the decreasing capacity of your laptop's battery over time.

Further Reading

It is important to note, however, that this USB-C power meter is not a surge protector; if you use a truly bad USB charger or cable, it will still fry the meter, and possibly the connected laptop/smartphone, depending on how the meter's innards are wired. I did look to see if you can buy an inline USB surge protector, but came up empty handed; there are tons of power strips with 120/240V plug sockets, USB sockets, and surge protection, but those only protect you from external surges, rather than dodgy cables.

If you really want to test a new charger or cable before plugging it into an expensive device, your best bet is some DIYish electronics involving a breakout board and a multimeter. But there doesn't seem to be a plug-and-play version of that yet.

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Sebastian Anthony
Sebastian is the editor of Ars Technica UK. He usually writes about low-level hardware, software, and transport, but it is emerging science and the future of technology that really get him excited. Emailsebastian@arstechnica.co.uk//Twitter@mrseb

83 Reader Comments

I just don't see how a dongle like this would save anything. It's wired in parallel, not series, so it doesn't protect against overvoltage, wrong polarity or overcurrent. By the time you see too high numbers on the display it's most likely already too late.

If you really want to test a new charger or cable before plugging it into an expensive device, your best bet is some DIYish electronics involving a breakout board and a multimeter.

Actually, you just need that meter you pictured and some way to attach an arbitrary load. I haven't yet located a cheap USB-C female breakout-board but I'm interested in finding one. You'd put it in line identically to how I do with my USB-power-meter for testing regular cables.

Save money on a USB cable, but buy these other accessories just to play it safe?

Doesn't seem useful to me.

So I take it you've never purchased a USB cable and had it work badly?

I had a friend thought their phone was defective - they even got a new charger/cable from the local phone store (for a non-trivial cost) and it still took all night and half the morning to charge and would be dead by early afternoon with little use.

I tested the cable and charger they bought...charger seemed good but the cable was Chinese junk and only providing a fraction of the power it was supposed to. Gave them one of my tested known-good cables and suddenly their phone charged in just over an hour and lasted all day.

So yeah, even if you don't "save money on a USB cable" you still might need the tool to test it.

If you really want to test a new charger or cable before plugging it into an expensive device, your best bet is some DIYish electronics involving a breakout board and a multimeter.

Actually, you just need that meter you pictured and some way to attach an arbitrary load. I haven't yet located a cheap USB-C female breakout-board but I'm interested in finding one. You'd put it in line identically to how I do with my USB-power-meter for testing regular cables.

I don't know enough about the USB-C spec to know if there's a simple USB-C-female to USB-A-female adapter I can plug-and-play or if I need a breakout board and have to test several pins.

I think the problem is that you don't get anything if you simply put a multimeter on the end of a USB cable. You have to negotiate with the charger (host) first, and then it sends you some electricity. Thus, you need some kind of breakout board with a USB controller on there, or something like that.

I just don't see how a dongle like this would save anything. It's wired in parallel, not series, so it doesn't protect against overvoltage, wrong polarity or overcurrent. By the time you see too high numbers on the display it's most likely already too late.

It may protect against reverse-polarity or over-voltage if you look at the readings before plugging it in. Over-current shouldn't be a problem, that's not up to the charger - it's up to the device (think how your wall outlet can provide 120V/240V at 15-20 amps but it won't "blow up" a 60 watt bulb which would be only 0.5A at 120V or 0.25A at 240V)

What it could be good for, testing a cable with a "dummy load" (light bulbs, resistors, etc) before you use it on your device to verify it's up to spec.

An Milliamp Hour(mAh) is a unit for measuring electric power over time.

"Over time" can be taken two ways: "divided by time" and "measured over a period of time". The first might be more "jargon".

===================

Edit:

One quote is: "Measure the power input to your device over time (in mAh)" (Amazon copy).

It isn't really reasonable to interpret this as "time/power" (the "mAh" disambiguates it as well).

The text in one of the pictcures is "MILLIAMP HOUR (power over time)". I wouldn't interpret that to mean "power/time" and anybody who did interpret it that way really wouldn't understand the correct interpretation).

USB-C power meter could save your devices from dodgy cables and chargers

Quote:

It is important to note, however, that this USB-C power meter is not a surge protector; if you use a truly bad USB charger or cable, it will still fry the meter, and possibly the connected laptop/smartphone, depending on how the meter's innards are wired.

Something to keep in mind is the milliamp hour capacity measurement still won't give you the actual capacity of the battery. It can give you the effective capacity, but not the actual. The DC voltage conversion circuitry has a certain efficiency, the battery design impacts efficiency of discharge, the rate of discharge impacts things, the length of the USB cable GREATLY impacts efficiency, as does the gauge of the wiring.

A 2amp current pulled on a 2 meter 28ga cable is going to see a huge amount of power loss by the time it gets to the power meter thingy. To lazy to pull up a calculator, but figure probably in the 20-30% range.

By comparison a .5a draw on a 1ft 26ga cable might see only a 5-6% loss.

And that is just the power loss due to the cable.

Figure the DC-DC conversion circuitry (3.2 to 5v, or is a big battery it might be 7.4v to 5v if dual cell), moderate discharge rate (about C2, or 1/2 the capacity per hour, so a 10wh battery would be discharged at 5 watts, a 20wh at 10w, etc.) and you are maybe looking at around 10% loss over label capacity assuming zero cable loss.

So figure a 5000mah battery would have a usable capacity of about 4500mah. Figure about 10% loss on the other end of a device being charged. So you are down to about 4050mah on a 5000mah battery. Then cabling losses. Shorter the cable and the heavier the gauge the better. Also the lower charge rate the better. Probably assume about a 15% cabling loss for a fairly typical 1 meter 26/28ga cable with a typical 1-2A load.

You are now down to about 3440mah out of a 5000mah battery pack.

Just some food for thought on realizable charge from a battery pack.

It is part of the reason for my portable battery packs I use 1ft 26ga USB cables as that gets me back a fair amount of power and I can place the pack wherever the heck it needs to be to charge the device. Not that it is usually possible, but I also try to charge at the lowest rate possible (one of my battery packs has a .5A and a 1.5A port, the other one has a 1A and a 2A port), which gets another couple of percent capacity back.

An Milliamp Hour(mAh) is a unit for measuring electric power over time.

"Over time" can be taken two ways: "divided by time" and "measured over a period of time". The first might be more "jargon".

I'm assuming that's probably marketers who don't know engineering and are trying to explain that it is "power over time" (correct) but not comprehending they wrote it as "power divided by time" (wrong)

I recently tested a LiPo jump start pack that had me super-excited bragging 12V and 8000mAh. My testing showed it was only measuring up to about 2.5Ah before it was dead. Took it apart and found 3 cells in series and while they had no markings based on physical size I hypothesize the marketing people said "oh 3 battery cells, add the capacities" even though it doesn't work that way. Wouldn't you know - 8/3=2.6 which is VERY close to my 2.5 measurement. So I think the engineers put it in series to get 12V 2.6Ah and the marketers added up both sets of numbers to boast a bigger number for the packaging even though it's wrong.

It's a cute enough unit on its own merits, but I can't think of a more dire indictment of the state of USB than to carry around a series dongle for your devices to ensure that you won't fry them with an off-standard charger. Or even that you need to carry said dongle as a diagnostic device, to know on a day-to-day basis what your port is actually doing.

I'm not sure what path the Implementers Forum could have taken to ensure that we didn't end up here, but it sure feels like there must have been a better option.

While power meters like this are pretty cool they won't save you from defective cables. I have an older micro usb one which is pretty cool for finding out how much usb wall warts lie (10W you say .... power meter says you are using 'alternate facts').

The infamous defective cables which blew up laptops were wired wrong. No power meter is going to save you from that. Now maybe it would blow up the power meter but more likely it would just blow up the power meter and the laptop.

I would point out the defective cables were all legacy USB-A to USB-C. Now I would strongly recommend NEVER connecting a USB-A to USB-C cable to a laptop and a legacy USB-A charger. If you don't do that you won't be exploding your laptops. For those who are worried, this site was created by redditors who compiled the results of that google engineer who tested cables:https://usbccompliant.com/

If you really want to test a new charger or cable before plugging it into an expensive device, your best bet is some DIYish electronics involving a breakout board and a multimeter.

Actually, you just need that meter you pictured and some way to attach an arbitrary load. I haven't yet located a cheap USB-C female breakout-board but I'm interested in finding one. You'd put it in line identically to how I do with my USB-power-meter for testing regular cables.

I don't know enough about the USB-C spec to know if there's a simple USB-C-female to USB-A-female adapter I can plug-and-play or if I need a breakout board and have to test several pins.

I think the problem is that you don't get anything if you simply put a multimeter on the end of a USB cable. You have to negotiate with the charger (host) first, and then it sends you some electricity. Thus, you need some kind of breakout board with a USB controller on there, or something like that.

At least, that's how I understand it!

Is this a new "feature" of USB-C?

I have to admit I know basically nothing about the new USB-C standard (I don't have anything that uses it) but I know the old cables were "dumb cables" as were the "chargers" (dumb power supplies)...so you could attach a light-bulb to the right pins and it would get power.

It's quite possible there's more to the new USB-C, I am very interested in learning about it and getting my hands on some gear to play with but that will have to wait until I have more free time (I'm a software engineer by trade) and save up some extra money to splurge (being an adult isn't fun, comes with pesky adult bills and adult responsibility).

If there's some document that explains any "handshaking" that goes on and how to get arbitrary power from USB-C I would be eager to read thru it; I simply haven't got to hunting down such a thing yet.

EDIT: I do know "once upon a time" there was supposed to be "handshaking" in normal USB but I am yet to personally find a device I own that "obeys" this. Most/all of my computers will happily provide 1.5-2.5 amps out the USB-A jack with the data pins un-connected and my phones/tablet (Android) seem happy to charge at near 2A with the data pins un-connected. So I know with my small sample of things (which may not be working "to spec") there isn't any extra "circuitry" to make them provide or consume power.

If you really want to test a new charger or cable before plugging it into an expensive device, your best bet is some DIYish electronics involving a breakout board and a multimeter.

Actually, you just need that meter you pictured and some way to attach an arbitrary load. I haven't yet located a cheap USB-C female breakout-board but I'm interested in finding one. You'd put it in line identically to how I do with my USB-power-meter for testing regular cables.

I don't know enough about the USB-C spec to know if there's a simple USB-C-female to USB-A-female adapter I can plug-and-play or if I need a breakout board and have to test several pins.

I think the problem is that you don't get anything if you simply put a multimeter on the end of a USB cable. You have to negotiate with the charger (host) first, and then it sends you some electricity. Thus, you need some kind of breakout board with a USB controller on there, or something like that.

At least, that's how I understand it!

Is this a new "feature" of USB-C?

I have to admit I know basically nothing about the new USB-C standard (I don't have anything that uses it) but I know the old cables were "dumb cables" as were the "chargers" (dumb power supplies)...so you could attach a light-bulb to the right pins and it would get power.

It's quite possible there's more to the new USB-C, I am very interested in learning about it and getting my hands on some gear to play with but that will have to wait until I have more free time (I'm a software engineer by trade) and save up some extra money to splurge (being an adult isn't fun, comes with pesky adult bills and adult responsibility).

If there's some document that explains any "handshaking" that goes on and how to get arbitrary power from USB-C I would be eager to read thru it; I simply haven't got to hunting down such a thing yet.

EDIT: I do know "once upon a time" there was supposed to be "handshaking" in normal USB but I am yet to personally find a device I own that "obeys" this. Most/all of my computers will happily provide 1.5-2.5 amps out the USB-A jack with the data pins un-connected and my phones/tablet (Android) seem happy to charge at near 2A with the data pins un-connected. So I know with my small sample of things (which may not be working "to spec") there isn't any extra "circuitry" to make them provide or consume power.

AFAIK everything beyond the lowest power level (100mA @ 5V) of the original USB spec requires a minimum level of signaling (by applying various pull up/down resistors to control wires); but that it's the sort that can be done with fixed resistors and doesn't need a micro controller.

If you really want to test a new charger or cable before plugging it into an expensive device, your best bet is some DIYish electronics involving a breakout board and a multimeter.

Actually, you just need that meter you pictured and some way to attach an arbitrary load. I haven't yet located a cheap USB-C female breakout-board but I'm interested in finding one. You'd put it in line identically to how I do with my USB-power-meter for testing regular cables.

I don't know enough about the USB-C spec to know if there's a simple USB-C-female to USB-A-female adapter I can plug-and-play or if I need a breakout board and have to test several pins.

I think the problem is that you don't get anything if you simply put a multimeter on the end of a USB cable. You have to negotiate with the charger (host) first, and then it sends you some electricity. Thus, you need some kind of breakout board with a USB controller on there, or something like that.

At least, that's how I understand it!

Is this a new "feature" of USB-C?

Yes. usb-c will provide the normal 5V 2A (10W) of power just like prior versions of USB (passive resistors used to indicate max power). However to run at the new higher voltage levels (9V, 15V, 20V) and/or higher current the device and charger have to do a handshake.

Honestly it does work pretty well. The same charger that chargs my laptop @ 20V also charges my phone @ 5V. Honestly the usb-c blows up devices is pretty overblown. It was related to legacy usb-c to usb-a cables and was pretty shitty cables a year ago. It has cleaned up pretty well over the last year. Granted if USB IF had any balls it never would have been an issue but they have always been pretty inept at enforcing anything.

If you really want to test a new charger or cable before plugging it into an expensive device, your best bet is some DIYish electronics involving a breakout board and a multimeter.

Actually, you just need that meter you pictured and some way to attach an arbitrary load. I haven't yet located a cheap USB-C female breakout-board but I'm interested in finding one. You'd put it in line identically to how I do with my USB-power-meter for testing regular cables.

I don't know enough about the USB-C spec to know if there's a simple USB-C-female to USB-A-female adapter I can plug-and-play or if I need a breakout board and have to test several pins.

I think the problem is that you don't get anything if you simply put a multimeter on the end of a USB cable. You have to negotiate with the charger (host) first, and then it sends you some electricity. Thus, you need some kind of breakout board with a USB controller on there, or something like that.

At least, that's how I understand it!

Is this a new "feature" of USB-C?

I have to admit I know basically nothing about the new USB-C standard (I don't have anything that uses it) but I know the old cables were "dumb cables" as were the "chargers" (dumb power supplies)...so you could attach a light-bulb to the right pins and it would get power.

It's quite possible there's more to the new USB-C, I am very interested in learning about it and getting my hands on some gear to play with but that will have to wait until I have more free time (I'm a software engineer by trade) and save up some extra money to splurge (being an adult isn't fun, comes with pesky adult bills and adult responsibility).

If there's some document that explains any "handshaking" that goes on and how to get arbitrary power from USB-C I would be eager to read thru it; I simply haven't got to hunting down such a thing yet.

EDIT: I do know "once upon a time" there was supposed to be "handshaking" in normal USB but I am yet to personally find a device I own that "obeys" this. Most/all of my computers will happily provide 1.5-2.5 amps out the USB-A jack with the data pins un-connected and my phones/tablet (Android) seem happy to charge at near 2A with the data pins un-connected. So I know with my small sample of things (which may not be working "to spec") there isn't any extra "circuitry" to make them provide or consume power.

AFAIK everything beyond the lowest power level (100mA @ 5V) of the original USB spec requires a minimum level of signaling (by applying various pull up/down resistors to control wires); but that it's the sort that can be done with fixed resistors and doesn't need a micro controller.

Is that re-introduced on USB-C?

I know with USB2.0 and type-A connectors I can personally verify all my computers (desktop/laptop) that I own will put out at least 800mA most of them 1.5A or more with only the outer 2 power-pins connected...because I tested them connecting only a volt/amp meter and variable resistor. I tested a Dell laptop, 2 HP laptops, 1 Dell desktop, 2 Gigabyte white-box builds, WinBook tablet, and Asus Eee PC. The Dell laptop stopped providing power when I went too high and "reset" on a reboot of the machine; the Dell desktop crashed and rebooted when I went too high and the voltage dipped.

I agree what you're saying was SUPPOSED to happen...but my testing shows nothing I have tested that I personally own follows that rule.

If you really want to test a new charger or cable before plugging it into an expensive device, your best bet is some DIYish electronics involving a breakout board and a multimeter.

Actually, you just need that meter you pictured and some way to attach an arbitrary load. I haven't yet located a cheap USB-C female breakout-board but I'm interested in finding one. You'd put it in line identically to how I do with my USB-power-meter for testing regular cables.

I don't know enough about the USB-C spec to know if there's a simple USB-C-female to USB-A-female adapter I can plug-and-play or if I need a breakout board and have to test several pins.

I think the problem is that you don't get anything if you simply put a multimeter on the end of a USB cable. You have to negotiate with the charger (host) first, and then it sends you some electricity. Thus, you need some kind of breakout board with a USB controller on there, or something like that.

At least, that's how I understand it!

Is this a new "feature" of USB-C?

I have to admit I know basically nothing about the new USB-C standard (I don't have anything that uses it) but I know the old cables were "dumb cables" as were the "chargers" (dumb power supplies)...so you could attach a light-bulb to the right pins and it would get power.

It's quite possible there's more to the new USB-C, I am very interested in learning about it and getting my hands on some gear to play with but that will have to wait until I have more free time (I'm a software engineer by trade) and save up some extra money to splurge (being an adult isn't fun, comes with pesky adult bills and adult responsibility).

If there's some document that explains any "handshaking" that goes on and how to get arbitrary power from USB-C I would be eager to read thru it; I simply haven't got to hunting down such a thing yet.

EDIT: I do know "once upon a time" there was supposed to be "handshaking" in normal USB but I am yet to personally find a device I own that "obeys" this. Most/all of my computers will happily provide 1.5-2.5 amps out the USB-A jack with the data pins un-connected and my phones/tablet (Android) seem happy to charge at near 2A with the data pins un-connected. So I know with my small sample of things (which may not be working "to spec") there isn't any extra "circuitry" to make them provide or consume power.

AFAIK everything beyond the lowest power level (100mA @ 5V) of the original USB spec requires a minimum level of signaling (by applying various pull up/down resistors to control wires); but that it's the sort that can be done with fixed resistors and doesn't need a micro controller.

Is that re-introduced on USB-C?

I know with USB2.0 and type-A connectors I can personally verify all my computers (desktop/laptop) that I own will put out at least 800mA most of them 1.5A or more with only the outer 2 power-pins connected...because I tested them connecting only a volt/amp meter and variable resistor. I tested a Dell laptop, 2 HP laptops, 1 Dell desktop, 2 Gigabyte white-box builds, WinBook tablet, and Asus Eee PC. The Dell laptop stopped providing power when I went too high and "reset" on a reboot of the machine; the Dell desktop crashed and rebooted when I went too high and the voltage dipped.

I agree what you're saying was SUPPOSED to happen...but my testing shows nothing I have tested that I personally own follows that rule.

For legacy usb it isn't a handshake it is just passive resistor put between D+ and D- pins on the charger side. The DEVICE is suppose to read the resistance between D+ and D- to determine that max current the port/charger can safely supply. If the device doesn't do that you could end up in an overcurrent situation. So a port capable of 2A output would use a 200 Ohm resistor and the device could sense 200 Ohm resistance between D+ and D- and 'know' the port can supply 2A.

Now in your example it is you not the port which is violating the usb spec. You weren't reading the resistance across the D+ D- pin to "learn" the max current the port can safely handle. It seems OCP on the port side was preventing excessive current but that isn't something you should assume and if you get a cheaply made port you could blow the power supply on it.

Actually, you just need that meter you pictured and some way to attach an arbitrary load. I haven't yet located a cheap USB-C female breakout-board but I'm interested in finding one. You'd put it in line identically to how I do with my USB-power-meter for testing regular cables.

I don't know enough about the USB-C spec to know if there's a simple USB-C-female to USB-A-female adapter I can plug-and-play or if I need a breakout board and have to test several pins.

I think the problem is that you don't get anything if you simply put a multimeter on the end of a USB cable. You have to negotiate with the charger (host) first, and then it sends you some electricity. Thus, you need some kind of breakout board with a USB controller on there, or something like that.

At least, that's how I understand it!

Is this a new "feature" of USB-C?

I have to admit I know basically nothing about the new USB-C standard (I don't have anything that uses it) but I know the old cables were "dumb cables" as were the "chargers" (dumb power supplies)...so you could attach a light-bulb to the right pins and it would get power.

It's quite possible there's more to the new USB-C, I am very interested in learning about it and getting my hands on some gear to play with but that will have to wait until I have more free time (I'm a software engineer by trade) and save up some extra money to splurge (being an adult isn't fun, comes with pesky adult bills and adult responsibility).

If there's some document that explains any "handshaking" that goes on and how to get arbitrary power from USB-C I would be eager to read thru it; I simply haven't got to hunting down such a thing yet.

EDIT: I do know "once upon a time" there was supposed to be "handshaking" in normal USB but I am yet to personally find a device I own that "obeys" this. Most/all of my computers will happily provide 1.5-2.5 amps out the USB-A jack with the data pins un-connected and my phones/tablet (Android) seem happy to charge at near 2A with the data pins un-connected. So I know with my small sample of things (which may not be working "to spec") there isn't any extra "circuitry" to make them provide or consume power.

AFAIK everything beyond the lowest power level (100mA @ 5V) of the original USB spec requires a minimum level of signaling (by applying various pull up/down resistors to control wires); but that it's the sort that can be done with fixed resistors and doesn't need a micro controller.

Is that re-introduced on USB-C?

I know with USB2.0 and type-A connectors I can personally verify all my computers (desktop/laptop) that I own will put out at least 800mA most of them 1.5A or more with only the outer 2 power-pins connected...because I tested them connecting only a volt/amp meter and variable resistor. I tested a Dell laptop, 2 HP laptops, 1 Dell desktop, 2 Gigabyte white-box builds, WinBook tablet, and Asus Eee PC. The Dell laptop stopped providing power when I went too high and "reset" on a reboot of the machine; the Dell desktop crashed and rebooted when I went too high and the voltage dipped.

I agree what you're saying was SUPPOSED to happen...but my testing shows nothing I have tested that I personally own follows that rule.

For legacy usb it isn't a handshake it is just passive resistors on the charger size which indicate to the device the max load. Without it you could end up in an overcurrent situation. A phone tries to pull 2A off a charger which can't handle more than 0.5A. At best OCP steps in and the charger shuts off. At worst (and more likely since chargers are built cheap) it overheats the charger and you have a fire.

So there is no digital handshake in legacy usb if that is what you are asking but there is resistor sense which lets the device know the max current the charger can supply.

Yeah, cheap chargers the typical results I see is they will either get really hot and sag in voltage (probably unprotected) or the slightly fancier ones they will simply cut off and not provide power until they are unplugged for a few minutes.

This also seems to apply to some of the "real" chargers that come with stuff these days for what that's worth. My current fav is the Anker multi-port charge stations, my "test supply" for cables is their 6-port 60-watt charge station that seems happy to put out 3A on a single port but clearly has some sort of protection because when you go past "some point" or if it shorts the port will "shut off" until you unplug the unit for a minute. It also seems to be "smart" in that it won't shut off if you "ramp up" to 3A but it will shut off if you connect a large load right from the start.

P.S. ArsTechnica staff - I think your site has a problem, I keep getting logged off and have a 50% success rate logging back in again the last 10 minutes or so

An Milliamp Hour(mAh) is a unit for measuring electric power over time.

"Over time" can be taken two ways: "divided by time" and "measured over a period of time". The first might be more "jargon".

I read initially read it as power / time (as in watts / secs) which is clearly not correct. Took me a second to figure out what they actually meant ("integrated over a period of time").

The "over time" isn't what bothers me, it's that they describe milliamp-hours as "power". Milliamps are a unit of current. Power is measured in Watts, and that would be the product of both the current and the voltage.

An Milliamp Hour(mAh) is a unit for measuring electric power over time.

"Over time" can be taken two ways: "divided by time" and "measured over a period of time". The first might be more "jargon".

I read initially read it as power / time (as in watts / secs) which is clearly not correct. Took me a second to figure out what they actually meant ("integrated over a period of time").

Missing the point.

Amps, or in this case milliamps, are a measure of electric current, not power. While this device does also indicate voltage, allowing power to be derived (at least if the voltage remains constant), that doesn't change the fact of the label being wrong.

I bet that also explains my non-working IMG tag then. The website it's hosted on (a server I rent and admin) has HTTPS support but I'm too cheap to shell out for a cert so it's self-signed. Maybe one day I'll get a proper cert.

An Milliamp Hour(mAh) is a unit for measuring electric power over time.

"Over time" can be taken two ways: "divided by time" and "measured over a period of time". The first might be more "jargon".

I'm assuming that's probably marketers who don't know engineering and are trying to explain that it is "power over time" (correct) but not comprehending they wrote it as "power divided by time" (wrong)

I recently tested a LiPo jump start pack that had me super-excited bragging 12V and 8000mAh. My testing showed it was only measuring up to about 2.5Ah before it was dead. Took it apart and found 3 cells in series and while they had no markings based on physical size I hypothesize the marketing people said "oh 3 battery cells, add the capacities" even though it doesn't work that way. Wouldn't you know - 8/3=2.6 which is VERY close to my 2.5 measurement. So I think the engineers put it in series to get 12V 2.6Ah and the marketers added up both sets of numbers to boast a bigger number for the packaging even though it's wrong.

That's misleading to the point that advertising standards should be contacted and a refund demanded. Wow, you don't often see that kind of naked deception, even with battery packs.

If you really want to test a new charger or cable before plugging it into an expensive device, your best bet is some DIYish electronics involving a breakout board and a multimeter.

Actually, you just need that meter you pictured and some way to attach an arbitrary load. I haven't yet located a cheap USB-C female breakout-board but I'm interested in finding one. You'd put it in line identically to how I do with my USB-power-meter for testing regular cables.

I don't know enough about the USB-C spec to know if there's a simple USB-C-female to USB-A-female adapter I can plug-and-play or if I need a breakout board and have to test several pins.

I think the problem is that you don't get anything if you simply put a multimeter on the end of a USB cable. You have to negotiate with the charger (host) first, and then it sends you some electricity. Thus, you need some kind of breakout board with a USB controller on there, or something like that.

At least, that's how I understand it!

Is this a new "feature" of USB-C?

I have to admit I know basically nothing about the new USB-C standard (I don't have anything that uses it) but I know the old cables were "dumb cables" as were the "chargers" (dumb power supplies)...so you could attach a light-bulb to the right pins and it would get power.

It's quite possible there's more to the new USB-C, I am very interested in learning about it and getting my hands on some gear to play with but that will have to wait until I have more free time (I'm a software engineer by trade) and save up some extra money to splurge (being an adult isn't fun, comes with pesky adult bills and adult responsibility).

If there's some document that explains any "handshaking" that goes on and how to get arbitrary power from USB-C I would be eager to read thru it; I simply haven't got to hunting down such a thing yet.

EDIT: I do know "once upon a time" there was supposed to be "handshaking" in normal USB but I am yet to personally find a device I own that "obeys" this. Most/all of my computers will happily provide 1.5-2.5 amps out the USB-A jack with the data pins un-connected and my phones/tablet (Android) seem happy to charge at near 2A with the data pins un-connected. So I know with my small sample of things (which may not be working "to spec") there isn't any extra "circuitry" to make them provide or consume power.

AFAIK everything beyond the lowest power level (100mA @ 5V) of the original USB spec requires a minimum level of signaling (by applying various pull up/down resistors to control wires); but that it's the sort that can be done with fixed resistors and doesn't need a micro controller.

Is that re-introduced on USB-C?

I know with USB2.0 and type-A connectors I can personally verify all my computers (desktop/laptop) that I own will put out at least 800mA most of them 1.5A or more with only the outer 2 power-pins connected...because I tested them connecting only a volt/amp meter and variable resistor. I tested a Dell laptop, 2 HP laptops, 1 Dell desktop, 2 Gigabyte white-box builds, WinBook tablet, and Asus Eee PC. The Dell laptop stopped providing power when I went too high and "reset" on a reboot of the machine; the Dell desktop crashed and rebooted when I went too high and the voltage dipped.

I agree what you're saying was SUPPOSED to happen...but my testing shows nothing I have tested that I personally own follows that rule.

Given the horrible results that Benson Leung when he started testing the first A-C cables a year or two ago, I wouldn't be surprised to learn that the situation with USB1/2 cables was/is equally fubared relative to the spec. His crusade does seem to have gotten most of the companies doing the actual manufacturing for anyone willing to slap their name on someone else's cables to fix the new problems from A to C cables that tell the device it's got a USB-C charger with support for higher power levels than an A charger can safely produce. OTOH I don't know if he's done any testing about behavior at lower power levels.

How can anything listed here protect against a USB killer device? It takes the power supplied and steps it up until it reaches a certain voltage and then dumps the stored energy on the data signals. If it doesn't get much power the actions will just take longer _and_ power have to be supplied by default or otherwise USB devices can't connect at all.

It's a cute enough unit on its own merits, but I can't think of a more dire indictment of the state of USB than to carry around a series dongle for your devices to ensure that you won't fry them with an off-standard charger. Or even that you need to carry said dongle as a diagnostic device, to know on a day-to-day basis what your port is actually doing.

I'm not sure what path the Implementers Forum could have taken to ensure that we didn't end up here, but it sure feels like there must have been a better option.

Not mixing in everything up to 60W with the default base level standard would've been a good start.

I bet that also explains my non-working IMG tag then. The website it's hosted on (a server I rent and admin) has HTTPS support but I'm too cheap to shell out for a cert so it's self-signed. Maybe one day I'll get a proper cert.

Try Let's Encrypt: free, automatic, and supported by all major browsers. You probably don't need extended validation just for your personal site, and LE is designed to fill the gap.

How can anything listed here protect against a USB killer device? It takes the power supplied and steps it up until it reaches a certain voltage and then dumps the stored energy on the data signals. If it doesn't get much power the actions will just take longer _and_ power have to be supplied by default or otherwise USB devices can't connect at all.

It's a cute enough unit on its own merits, but I can't think of a more dire indictment of the state of USB than to carry around a series dongle for your devices to ensure that you won't fry them with an off-standard charger. Or even that you need to carry said dongle as a diagnostic device, to know on a day-to-day basis what your port is actually doing.

I'm not sure what path the Implementers Forum could have taken to ensure that we didn't end up here, but it sure feels like there must have been a better option.

Not mixing in everything up to 60W with the default base level standard would've been a good start.

Why?

I would hate to have 10W cables, 15W cables, 27W cables, 45W cables and 60W cables. All the cables can support 3A and thus they can support 60W (3@ @ 20V) so require them to support 3A.

Anything above that requires larger guage wires so it is relegated to a seperate class of cables and uses a method to id itself (use a 3A cable in a 5A charger and both the charger and device will recognize the max current allowed is 3A). Honestly I just wish they mandated the larger wires and made all USB cables support 5A and thus all wattage up the spec max of 100W but I imagine >60W chargers will be rare so I can understand they limited it to 60W.

I want to point out a factual error: USB Authentication will NOT protect you from USB Killer-type devices, and it can't protect you from improperly constructed cables either. USB Authentication is a certificate-based mechanism that enables a host to use either USB data or USB Power Delivery to authenticate a device/charger. By definition, this requires a valid data and power connection.

The dangerous USB-C cable that blew up Benson's Chromebook was most certainly not wired correctly...the power and ground connections were reversed because the manufacturer of that cable did not review the USB Specification and did not even test their product before shipping it. Mis-wiring anything can be quite dangerous and it's not necessarily the fault of the spec if it happened due to an individual's carelessness.

The USB Killer device doesn't have any USB capabilities whatsoever...it literally just takes power provided by a USB port and charges up its weapon. Beyond the initial insertion detection, your computer/charger/hub won't know what the connected device is, and it has NO WAY OF KNOWING. The USB Killer is literally a blunt weapon that tries to repeatedly, physically damage high speed signaling wires. The USB "vulnerability" that is "exploited" by the USB Killer is brute force...it's exactly the same thing as saying that the human skull is "vulnerable" to sufficient blunt force trauma.

USB Authentication CAN protect you by being able to spot counterfeit/improperly configured/known bad products if they support USB Authentication and you have enacted such a system policy.

I want to point out a factual error: USB Authentication will NOT protect you from USB Killer-type devices, and it can't protect you from improperly constructed cables either. USB Authentication is a certificate-based mechanism that enables a host to use either USB data or USB Power Delivery to authenticate a device/charger. By definition, this requires a valid data and power connection.

The dangerous USB-C cable that blew up Benson's Chromebook was most certainly not wired correctly...the power and ground connections were reversed because the manufacturer of that cable did not review the USB Specification and did not even test their product before shipping it. Mis-wiring anything can be quite dangerous and it's not necessarily the fault of the spec if it happened due to an individual's carelessness.

The USB Killer device doesn't have any USB capabilities whatsoever...it literally just takes power provided by a USB port and charges up its weapon. Beyond the initial insertion detection, your computer/charger/hub won't know what the connected device is, and it has NO WAY OF KNOWING. The USB Killer is literally a blunt weapon that tries to repeatedly, physically damage high speed signaling wires. The USB "vulnerability" that is "exploited" by the USB Killer is brute force...it's exactly the same thing as saying that the human skull is "vulnerable" to sufficient blunt force trauma.

The USB Killer won't receive any power from the port, because it can't authenticate... so the host machine never sends power to the USB Killer. Right?